Asymptotic safety and the "no boundary" proposal

[tom.stoer]

Does anybody know papers in which the asymptotic safety approach has been applied to the "no boundary" proposal?

 

[Haelfix]

Hey Tom,

It's a little difficult to know what you mean by this. First do you mean, asymptotic safety in the sense of Weinberg applied to gravity (eg nonperturbative renormalizability), or the modern program that takes truncations of the functional exact renormalization group equations (they are not necessarily the same thing, the second could be false but the first could be true).

Further, the no boundary proposal is usually formulated in the old approaches to quantum cosmology (really it's more about initial conditions in the minisuperspace approach to canonical quantum gravity) although it is often (not necessarily equivalently) formulated as a Euclidean path integral problem (where again the choice of the boundary conditions defines the proposal). Usually the assumption of semiclassical gravity is implicit, and it is rare that matter is included (it makes an already intractable calculation even more difficult), so its a little difficult to see what you mean.

 

[member 11137]

Do you refer to the Hawking's proposition? If yes: he spoke of it in his book "a short story of..." (I don't remember which page but, at this page, he gave the name of some colleague he worked with about that topic). Sorry it is a little bit vague but I have no better hint.

 

[member 11137]

In my English version of "A brief history of time" (A Bantam book - 1988 - 0 553 17521 1), you get interesting information page 144. Sir S. W. Hawking worked his "no boundary proposal" first at the University of California (Santa Barbara) with Jim Hartle and then in Cambridge with Julian Luttrel and Jonathan Halliwell. The implications of that proposal are again explored page 157; page 159, it is explained why and how a student of him (Raymond Laflamme) has prouved that that proposal was a mistake (disorder would continue to increase in contracting phases of the universe...). For more détails: see the book itself and Google the names of the authors cited here.